Making a wise generator choice?

ligwydligwyd Registered Users Posts: 191 ✭✭
edited December 2018 in Solar Beginners Corner #1
I'm sure this topic has been beaten to death simply based on system design requirements, fuel source, budget, reliability etc.
However, Is there a "10 commandments" to generator selection when designing an off grid power system?
Originally I liked the idea of a smaller lower rpm Kubota powered diesel generator due to quality/ longevity and best bang (most power) for your buck with fuel consumption.
Now I am considering the possible continual refilling mess (guess that could be mitigated with an external fuel tank) and that It may not run enough to justify spending the cash on a prime generator (designed for round the clock usage). Then again you'd only buy it once and you could pass it on to the boy.
Questions many have already been through that I am hoping to lean from.
Appreciate any input that others may have to add to this topic.
Thank you :)


  • EstragonEstragon Registered Users Posts: 4,496 ✭✭✭✭✭
    A good discussion:

    IMHO, a good generator is worth the investment in many (but not all) off-grid situations.  In some, more southern climates, folks are blessed with reasonable solar year-round.  In my case, solar is pretty reliably unreliable from ~Oct to Jan between low sun angle, short days, and seasonably gloomy weather.  A smallish low RPM diesel (c.1982) does the job for me in that period.
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mcnutt13579mcnutt13579 Registered Users Posts: 110 ✭✭✭
    Where are you located and how much do you expect to use the generator are the most important questions here.
  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited December 2018 #4
    Also consider propane.    And capturing the waste heat for the house (space heating and/or hot water).

    I am available for custom hardware/firmware development

  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Will you be integrating the generator with a charger or an inverter/charger ?

    I am fairly happy with a 3kw slow speed diesel generator.  Fuel is about as universal as it gets. Crankcase oil is the long term show stopper.

    My basic house loads are 300w roughly, and the generator will run the pump and start the fridge.   I dont have air conditioning.

    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    gen: ,

  • softdownsoftdown Solar Expert Posts: 3,630 ✭✭✭✭
    While I have a good diesel generator I still lust for a propane genset. Diesel doesn't cotton to very cold weather and that is exactly when solar is most likely to come up short. Diesel is also loud and somewhat expensive for fuel and very expensive if significant repairs are needed. 

    Propane is often cheap if bought in quantity in August. Last forever, burns clean, doesn't clog carb jets, and doesn't mind the cold. Not saying propane is for everybody but it is worth considering for many.

    For very heavy usage? Then low rpm diesel shines like the sun.

    I live in a very sunny alpine desert so my perspective is often unique from those who suffer from cloudy winters in the frozen north. They may take heart in the fact that I find northern folks to often be a cut above their southern brethren. #QualityMatters
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • t00lst00ls Solar Expert Posts: 239 ✭✭✭
    oh my ..the generator discussion

    pro: low fuel consumption
    con: loud, needs the oil changed a lot, not good in cold weather

    pro: you can convert to tri-fuel using NG and LPG along with regular gas, easy to maintain, works in all weather
    cons: uses a lot of gas when running on gasoline

    sizing: depends on the loads you want to run, cant go wrong with at least 3500w continuous

    also depends on if you have an inverter that incorporates generator power....size it just above the inverter size because most generators like to run at half load efficiently

    watch out for advertising....7000w, when in reality that is probably the surge rating for so many seconds

    look for the continuous output rating

    as an alternative to a backup generator for charging batteries on a cloudy day, if you have a creek, you can do micro-hydro, if there is enough flow or head
    if you have a lot of windy days, build a hugh piggot type wind turbine oldies/Hugh Piggott Axial-flow PMG wind turbine May 2003.pdf

    good luck

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